how to make a bump texture in blender?
To fake relief on a surface you use a bump map, where the bright parts of the images will look as if they are sticking out of the surface.

For example in cycles. This plane with only 4 vertex shows fake relief.


Keep in mind that this is just a texture and if you look at it from the side it reveals the lack of height or real geometry.



For Blender internal the important setting is setting the normal as influence for the texture's image.